A 53-year-old woman presented with idiopathic thrombocytopenic purpura (ITP) that was refractory to corticosteroid therapy. Her bleeding had worsened gradually due to prolonged thrombocytopenia, but her low platelet count after high-dose intravenous gamma globulin therapy contraindicated a splenectomy. We therefore decided to perform a partial splenic embolization (PSE). The patient's platelet count increased gradually thereafter, allowing us to safely perform a splenectomy. We concluded that PSE is a useful preoperative procedure, especially for patients with ITP that is refractory to high-dose intravenous gamma-globulin therapy. Moreover, it is possible to predict the effects of a splenectomy preoperatively if the PSE procedure is used.